Described below is a device for determining a torque which acts on a drive shaft. The drive shaft can be, for example, a shaft between a motor and a working machine, via which a torque from the motor is transmitted to the drive machine. Also described is a method for determining the torque.
The registration of a torque on a shaft or on a coupling for such a shaft is applied in industrial drive technology, in power technology, in web drives and in automobile technology. In one embodiment of torque sensors, the determination of the torque is carried out without contact. Here, a signal correlated with a direction or magnitude of the torque is transferred from the rotating parts (shaft or coupling) to a fixed sensor, for example via an air gap. Thus, no wearing parts, such as wiping contacts, for example, have to be used. This considerably increases the reliability of the sensors.
A signal correlated with the transmitted torque can be generated by a magnetic device which is fixed to the shaft and which generates a magnetic field. This magnetic field is measured by a magnetic field sensor arranged in a stationary manner in the vicinity of the shaft and is processed further by suitable electronics. The magnetic field sensors used are Hall sensors or sensors which are based on the AMR effect (anisotropic magnetoresistive effect). The disadvantage with a magnetic field-based torque sensor is that the magnetic field sensors used generate highly fluctuating signals even in the case of a constant torque. Therefore, a relatively high expenditure on switching is necessary in order to determine a torque with a magnetic field-based torque sensor reliably.